Asthma is the most common chronic disease for youth in industrialized countries. Despite advances in medical treatments, the prevalence of asthma in youth continues to rise, resulting in a significant burden on society in terms of financial costs and lost productivity due to missed school days. Thus, there is a need to identify modifiable health behaviors, such as sleep duration, that may reduce the frequency and severity of asthma exacerbations. Chronic partial sleep restriction (routinely sleeping less than required for optimal functioning) is common among adolescents, including youth with asthma, and is often behaviorally induced. Growing evidence has shown that chronic partial sleep restriction contributes to disease development and poorer health outcomes. For adolescents with asthma, chronic partial sleep restriction may result in poorer lung function and functional outcomes. Therefore, increased sleep duration may provide a novel, effective, low-cost intervention for the clinical management of asthma in adolescents. This project brings together investigators with substantial expertise in pediatric sleep, asthma, and immunology and will enroll 86 adolescents (ages 12-17 years) with asthma to participate in an established sleep manipulation protocol. Following a week of baseline sleep stabilization, adolescents with asthma will participate in a randomized, counterbalanced design that includes two experimentally manipulated weeks of sleep duration - one week of a deficient sleep opportunity (6.5 hours in bed per night) and one week of a healthy sleep opportunity (10 hours in bed per night). Subjects will complete both objective and subjective daily measures of sleep (actigraphy, sleep diary), as well as asthma control and lung function (electronic peak expiratory flow, asthma diary). Additional measures of lung function (spirometry), asthma control, health related quality of life, and inflammation (exhaled nitric oxide, serum cytokines) will be collected at the end of each study week. The aim of this study is to examine the impact of chronic partial sleep restriction vs. healthy sleep opportunity on lung function and functional outcomes in adolescents with asthma. An exploratory aim will examine the impact of chronic partial sleep restriction vs. healthy sleep opportunity on biomarkers of inflammation in adolescents with asthma. The proposed study would be the first to use an experimental manipulation of sleep duration in adolescents with asthma, and allows our team of pediatric experts to examine the causal impact of sleep duration on lung function and functional outcomes. In addition, this study will utilize objective measures of sleep duration, lung function, and inflammation (rather than relying on self-report measures), as well as standardized outcome measures of asthma control and health related quality of life. Finally, the protocol design closely mimics the chronic partial sleep deficiency experienced by many adolescents on school nights, promoting confidence that the findings will have real-world relevance and applicability in the clinical care for adolescents with asthma.